Re: Plan targetlists in EXPLAIN output

"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

> I'm not convinced. The width is often useful to understand why the
> planner did something (eg, chose a hash plan or not). The exact
> contents of the targetlist are usually not nearly as interesting.

I've never seen a single post on any of the lists where anyone went through
that exercise though.

> -> Seq Scan on tenk1 (cost=0.00..458.00 rows=10000 width=4)
> Output: unique1, unique2, two, four, ten, twenty, hundred, thousand, twothousand, fivethous, tenthous, odd, even, stringu1, stringu2, string4

I wonder if I even understand what width means. Or does the planner think most
of these columns are mostly null?

Or is it estimating the width based on the belief that only the thousand
column is actually going to be emitted?

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
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